You're not hallucinating. That's a "2" next to the dollar sign on your local gas station's price board.

The average price for regular gasoline in the Allentown area has fallen below the $3-a-gallon mark for the first time in almost four years, according to GasBuddy.com.

The $2.87 price for regular posted at the Turkey Hill gas station/mini-market in Coopersburg — one of the lowest in the Valley on Monday — was enough to make Gerber Romero tap his brakes and pull in for a refill on his way home from Philadelphia.

"That's why I'm filling up," Romero said. "I saw $2.87. I said this is great. I haven't seen these kind of prices in a long time."

Likely spurred by free-market competition, three gas stations along Route 309 in the borough posted prices of $2.87 per gallon Monday, while US Gas offered cash customers $2.86, putting it at the top of the list of cheap Lehigh Valley petrol.

CRAIG LARIMER, THE MORNING CALL

CRAIG LARIMER, THE MORNING CALL

The big question on drivers' minds as they filled up: How long will it stay this low?

Unless something dramatic happens, prices are not expected to rise significantly until spring, analysts say. Gas prices are cyclical. They typically bottom out between Thanksgiving and Christmas, then rise again early in the year as refineries switch to summer gas formulations.

This year, it appears that the bottom is simply coming a little bit earlier than usual.

"Prices will go up," said Patrick DeHaan, senior petroleum analyst with GasBuddy.com. "The tough part is calling today when the bottom is taking place. I think we may be close."

TIMOTHY FORD, THE MORNING CALL

The Turkey Hill Minit Market at 106 S 3rd Street in Coopersburg currently has some of the lowest gasoline prices in the area at 2.87 per gallon.

The Turkey Hill Minit Market at 106 S 3rd Street in Coopersburg currently has some of the lowest gasoline prices in the area at 2.87 per gallon. (TIMOTHY FORD, THE MORNING CALL)

For now, though, enjoy the savings. On Monday, the average price for regular gas in Lehigh County hit $2.99.5 while Northampton County prices hit $2.97.2. The 27-cent savings compared to the same time last year computes to $4.05 for every 15-gallon gas tank fill-up.

But those savings triple when compared with the May 2014 Allentown average of $3.77

For Mick Barberry of Quakertown, who was fueling up his Underdogs to the Rescue box truck, the savings are doggone significant. Barberry estimates he drives about 3,000 miles a week picking up rescue pups from shelters in the South and delivering them to local adoption groups.

"I fill this truck up five times over a week," he said, pumping gas into the 40-gallon tank at the Coopersburg Turkey Hill on Monday afternoon.

He's been passing the savings on to the organizations he serves.

Gas prices and underlying crude oil prices are in a bit of a sweet spot, DeHaan said. They're low enough to pump extra spending money into consumers' pockets, but not so low that U.S. oil companies decide they're losing money and shut down domestic drilling operations.

John Jenkins has plenty of uses for the money he's saving on every fill-up.

"I hope it keeps up," said Jenkins, 48, filling up at the Turkey Hill. "We are saving a lot right now. Mostly it is going toward other bills."

Multiple forces are driving down the price of crude oil, the main ingredient in gasoline.

The decline over the last few months has been driven by the Organization of Petroleum Exporting Countries, which has dropped its crude oil price to compete with increased U.S. production, DeHaan said.

U.S. oil production has surged in recent years thanks to new hydraulic fracturing, or fracking, technology.

Total U.S. crude oil production came close to 9 million barrels a day in the final week of October and is expected to average 9.5 million barrels in 2015, which would be the most since 1970, according to the U.S. Energy Information Administration.

Meanwhile, a slumping worldwide economy has depressed crude demand. And, critically, Saudi Arabia has reacted not by cutting oil production to prop up prices, but by reducing prices to maintain its market share. This left other members of OPEC, such as Iran and Iraq, with little choice but to follow suit.

If global oil prices stay low for an extended time, that could slow the growth of domestic oil production in certain areas of the country, but on the whole, low prices are good for the U.S. economy, said Rob Godby, director of the Center for Energy Economics & Public Policy at the University of Wyoming.

"It creates an immediate boost in our economy," he said. "Everybody feels it in the pocketbook and they are able to spend more. We are heading into the holiday season, what better timing?"

Enjoy it while you can, he said. It won't take much to send extremely volatile oil prices back up: "Another blow-up with Russia. Significant changes on the ground in the Middle East and let's face it, that's always possible."

Gas prices in this region — and across Pennsylvania — would have been even lower if not for a tax hike that Gov. Tom Corbett signed into law last year to fund a transportation bill.

On Jan. 1, wholesale gas taxes in Pennsylvania increased by 9.5 cents per gallon under the first phase of changes to the oil franchise tax, bringing the state's total gas tax to nearly 42 cents.